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	$207.71	7.710%	$223.7244	$223.72	$223.70	$223.70
Purchase #2	$161.26	3.492%	$166.8912	$166.89	$166.90	$166.90
Purchase #3	$241.90	10.835%	$268.1099	$268.11	$268.10	$268.10
Purchase #4	$55.62	6.503%	$59.237	$59.24	$59.25	$59.20
Purchase #5	$220.39	10.629%	$243.8153	$243.82	$243.80	$243.80
Purchase #6	$138.82	10.157%	$152.9199	$152.92	$152.90	$152.90
Purchase #7	$149.66	4.665%	$156.6416	$156.64	$156.65	$156.60
7 purchase totals =	$1,175.36		$1,271.3393	$1,271.34	$1,271.30	$1,271.20