Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$96.82	5.413%	$102.0609	$102.06	$102.05	$102.10
Purchase #2	$91.93	12.385%	$103.3155	$103.32	$103.30	$103.30
Purchase #3	$208.30	5.333%	$219.4086	$219.41	$219.40	$219.40
Purchase #4	$115.98	10.272%	$127.8935	$127.89	$127.90	$127.90
Purchase #5	$243.46	12.150%	$273.0404	$273.04	$273.05	$273.00
Purchase #6	$127.84	7.731%	$137.7233	$137.72	$137.70	$137.70
Purchase #7	$167.29	8.115%	$180.8656	$180.87	$180.85	$180.90
7 purchase totals =	$1,051.62		$1,144.3078	$1,144.31	$1,144.25	$1,144.30