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	$212.90	6.301%	$226.3148	$226.31	$226.30	$226.30
Purchase #2	$48.53	10.783%	$53.763	$53.76	$53.75	$53.80
Purchase #3	$189.64	5.600%	$200.2598	$200.26	$200.25	$200.30
Purchase #4	$188.90	5.166%	$198.6586	$198.66	$198.65	$198.70
Purchase #5	$99.69	12.261%	$111.913	$111.91	$111.90	$111.90
Purchase #6	$128.69	3.143%	$132.7347	$132.73	$132.75	$132.70
Purchase #7	$117.80	10.428%	$130.0842	$130.08	$130.10	$130.10
7 purchase totals =	$986.15		$1,053.7281	$1,053.71	$1,053.70	$1,053.80