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	$56.29	5.404%	$59.3319	$59.33	$59.35	$59.30
Purchase #2	$89.85	7.242%	$96.3569	$96.36	$96.35	$96.40
Purchase #3	$246.29	12.476%	$277.0171	$277.02	$277.00	$277.00
Purchase #4	$39.33	12.836%	$44.3784	$44.38	$44.40	$44.40
Purchase #5	$127.28	3.447%	$131.6673	$131.67	$131.65	$131.70
Purchase #6	$220.59	10.568%	$243.902	$243.90	$243.90	$243.90
Purchase #7	$41.55	7.659%	$44.7323	$44.73	$44.75	$44.70
7 purchase totals =	$821.18		$897.3859	$897.39	$897.40	$897.40