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	$218.97	4.694%	$229.2485	$229.25	$229.25	$229.20
Purchase #2	$130.68	4.375%	$136.3973	$136.40	$136.40	$136.40
Purchase #3	$58.63	5.109%	$61.6254	$61.63	$61.65	$61.60
Purchase #4	$33.77	4.600%	$35.3234	$35.32	$35.30	$35.30
Purchase #5	$99.44	11.859%	$111.2326	$111.23	$111.25	$111.20
Purchase #6	$82.51	9.789%	$90.5869	$90.59	$90.60	$90.60
Purchase #7	$181.33	6.474%	$193.0693	$193.07	$193.05	$193.10
7 purchase totals =	$805.33		$857.4834	$857.49	$857.50	$857.40