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	$182.74	8.399%	$198.0883	$198.09	$198.10	$198.10
Purchase #2	$112.43	10.693%	$124.4521	$124.45	$124.45	$124.50
Purchase #3	$96.87	13.288%	$109.7421	$109.74	$109.75	$109.70
Purchase #4	$72.40	7.528%	$77.8503	$77.85	$77.85	$77.90
Purchase #5	$243.62	8.743%	$264.9197	$264.92	$264.90	$264.90
Purchase #6	$141.66	13.320%	$160.5291	$160.53	$160.55	$160.50
Purchase #7	$86.49	3.119%	$89.1876	$89.19	$89.20	$89.20
7 purchase totals =	$936.21		$1,024.7692	$1,024.77	$1,024.80	$1,024.80