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	$208.98	12.610%	$235.3324	$235.33	$235.35	$235.30
Purchase #2	$25.92	5.843%	$27.4345	$27.43	$27.45	$27.40
Purchase #3	$134.91	4.781%	$141.36	$141.36	$141.35	$141.40
Purchase #4	$100.40	10.681%	$111.1237	$111.12	$111.10	$111.10
Purchase #5	$192.67	9.488%	$210.9505	$210.95	$210.95	$211.00
Purchase #6	$81.56	5.637%	$86.1575	$86.16	$86.15	$86.20
Purchase #7	$69.43	13.740%	$78.9697	$78.97	$78.95	$79.00
7 purchase totals =	$813.87		$891.3283	$891.32	$891.30	$891.40