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	$59.80	3.583%	$61.9426	$61.94	$61.95	$61.90
Purchase #2	$85.79	12.230%	$96.2821	$96.28	$96.30	$96.30
Purchase #3	$46.71	12.681%	$52.6333	$52.63	$52.65	$52.60
Purchase #4	$30.52	5.177%	$32.1	$32.10	$32.10	$32.10
Purchase #5	$217.46	9.629%	$238.3992	$238.40	$238.40	$238.40
Purchase #6	$238.90	10.596%	$264.2138	$264.21	$264.20	$264.20
Purchase #7	$87.46	4.510%	$91.4044	$91.40	$91.40	$91.40
7 purchase totals =	$766.64		$836.9754	$836.96	$837.00	$836.90