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	$79.71	11.700%	$89.0361	$89.04	$89.05	$89.00
Purchase #2	$89.66	7.552%	$96.4311	$96.43	$96.45	$96.40
Purchase #3	$133.59	6.784%	$142.6527	$142.65	$142.65	$142.70
Purchase #4	$121.87	3.479%	$126.1099	$126.11	$126.10	$126.10
Purchase #5	$185.95	9.344%	$203.3252	$203.33	$203.35	$203.30
Purchase #6	$234.98	12.603%	$264.5945	$264.59	$264.60	$264.60
Purchase #7	$98.27	4.704%	$102.8926	$102.89	$102.90	$102.90
7 purchase totals =	$944.03		$1,025.0421	$1,025.04	$1,025.10	$1,025.00