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	$89.47	4.725%	$93.6975	$93.70	$93.70	$93.70
Purchase #2	$233.98	13.162%	$264.7764	$264.78	$264.80	$264.80
Purchase #3	$180.78	6.197%	$191.9829	$191.98	$192.00	$192.00
Purchase #4	$96.59	13.645%	$109.7697	$109.77	$109.75	$109.80
Purchase #5	$53.83	11.380%	$59.9559	$59.96	$59.95	$60.00
Purchase #6	$145.80	6.557%	$155.3601	$155.36	$155.35	$155.40
Purchase #7	$48.33	13.780%	$54.9899	$54.99	$55.00	$55.00
7 purchase totals =	$848.78		$930.5324	$930.54	$930.55	$930.70