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	$169.58	4.302%	$176.8753	$176.88	$176.90	$176.90
Purchase #2	$128.96	4.278%	$134.4769	$134.48	$134.50	$134.50
Purchase #3	$28.25	12.830%	$31.8745	$31.87	$31.85	$31.90
Purchase #4	$166.67	3.385%	$172.3118	$172.31	$172.30	$172.30
Purchase #5	$89.38	7.717%	$96.2775	$96.28	$96.30	$96.30
Purchase #6	$170.33	10.427%	$188.0903	$188.09	$188.10	$188.10
Purchase #7	$234.45	3.790%	$243.3357	$243.34	$243.35	$243.30
7 purchase totals =	$987.62		$1,043.2420	$1,043.25	$1,043.30	$1,043.30