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	$208.33	7.224%	$223.3798	$223.38	$223.40	$223.40
Purchase #2	$54.54	9.227%	$59.5724	$59.57	$59.55	$59.60
Purchase #3	$36.89	7.111%	$39.5132	$39.51	$39.50	$39.50
Purchase #4	$239.76	12.177%	$268.9556	$268.96	$268.95	$269.00
Purchase #5	$50.36	5.292%	$53.0251	$53.03	$53.05	$53.00
Purchase #6	$66.91	8.709%	$72.7372	$72.74	$72.75	$72.70
Purchase #7	$191.47	10.346%	$211.2795	$211.28	$211.30	$211.30
7 purchase totals =	$848.26		$928.4628	$928.47	$928.50	$928.50