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	$127.84	10.719%	$141.5432	$141.54	$141.55	$141.50
Purchase #2	$28.36	11.151%	$31.5224	$31.52	$31.50	$31.50
Purchase #3	$128.67	9.819%	$141.3041	$141.30	$141.30	$141.30
Purchase #4	$249.45	12.501%	$280.6337	$280.63	$280.65	$280.60
Purchase #5	$13.57	11.747%	$15.1641	$15.16	$15.15	$15.20
Purchase #6	$122.67	3.557%	$127.0334	$127.03	$127.05	$127.00
Purchase #7	$80.44	10.586%	$88.9554	$88.96	$88.95	$89.00
7 purchase totals =	$751.00		$826.1563	$826.14	$826.15	$826.10