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	$92.69	6.170%	$98.409	$98.41	$98.40	$98.40
Purchase #2	$175.73	6.241%	$186.6973	$186.70	$186.70	$186.70
Purchase #3	$46.90	3.298%	$48.4468	$48.45	$48.45	$48.40
Purchase #4	$153.32	9.457%	$167.8195	$167.82	$167.80	$167.80
Purchase #5	$227.60	6.404%	$242.1755	$242.18	$242.20	$242.20
Purchase #6	$184.34	8.679%	$200.3389	$200.34	$200.35	$200.30
Purchase #7	$100.64	3.109%	$103.7689	$103.77	$103.75	$103.80
7 purchase totals =	$981.22		$1,047.6559	$1,047.67	$1,047.65	$1,047.60