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	$160.97	8.307%	$174.3418	$174.34	$174.35	$174.30
Purchase #2	$247.59	3.220%	$255.5624	$255.56	$255.55	$255.60
Purchase #3	$209.38	12.223%	$234.9725	$234.97	$234.95	$235.00
Purchase #4	$64.74	11.610%	$72.2563	$72.26	$72.25	$72.30
Purchase #5	$43.49	9.165%	$47.4759	$47.48	$47.50	$47.50
Purchase #6	$155.79	9.826%	$171.0979	$171.10	$171.10	$171.10
Purchase #7	$71.27	9.671%	$78.1625	$78.16	$78.15	$78.20
7 purchase totals =	$953.23		$1,033.8693	$1,033.87	$1,033.85	$1,034.00