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	$245.85	11.720%	$274.6636	$274.66	$274.65	$274.70
Purchase #2	$166.45	5.801%	$176.1058	$176.11	$176.10	$176.10
Purchase #3	$215.51	3.127%	$222.249	$222.25	$222.25	$222.20
Purchase #4	$249.76	11.860%	$279.3815	$279.38	$279.40	$279.40
Purchase #5	$39.31	12.711%	$44.3067	$44.31	$44.30	$44.30
Purchase #6	$57.46	6.834%	$61.3868	$61.39	$61.40	$61.40
Purchase #7	$81.95	11.814%	$91.6316	$91.63	$91.65	$91.60
7 purchase totals =	$1,056.29		$1,149.7250	$1,149.73	$1,149.75	$1,149.70