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	$211.71	5.410%	$223.1635	$223.16	$223.15	$223.20
Purchase #2	$126.60	3.627%	$131.1918	$131.19	$131.20	$131.20
Purchase #3	$193.74	9.732%	$212.5948	$212.59	$212.60	$212.60
Purchase #4	$200.51	7.375%	$215.2976	$215.30	$215.30	$215.30
Purchase #5	$144.37	5.567%	$152.4071	$152.41	$152.40	$152.40
Purchase #6	$67.29	6.757%	$71.8368	$71.84	$71.85	$71.80
Purchase #7	$78.33	9.360%	$85.6617	$85.66	$85.65	$85.70
7 purchase totals =	$1,022.55		$1,092.1533	$1,092.15	$1,092.15	$1,092.20