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	$100.71	3.872%	$104.6095	$104.61	$104.60	$104.60
Purchase #2	$210.82	3.772%	$218.7721	$218.77	$218.75	$218.80
Purchase #3	$218.52	5.112%	$229.6907	$229.69	$229.70	$229.70
Purchase #4	$82.34	11.814%	$92.0676	$92.07	$92.05	$92.10
Purchase #5	$148.93	5.119%	$156.5537	$156.55	$156.55	$156.60
Purchase #6	$185.78	11.671%	$207.4624	$207.46	$207.45	$207.50
Purchase #7	$80.63	3.389%	$83.3626	$83.36	$83.35	$83.40
7 purchase totals =	$1,027.73		$1,092.5186	$1,092.51	$1,092.45	$1,092.70