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	$103.74	7.740%	$111.7695	$111.77	$111.75	$111.80
Purchase #2	$71.46	8.292%	$77.3855	$77.39	$77.40	$77.40
Purchase #3	$181.73	13.237%	$205.7856	$205.79	$205.80	$205.80
Purchase #4	$6.76	11.340%	$7.5266	$7.53	$7.55	$7.50
Purchase #5	$209.88	11.497%	$234.0099	$234.01	$234.00	$234.00
Purchase #6	$235.29	12.108%	$263.7789	$263.78	$263.80	$263.80
Purchase #7	$235.39	3.805%	$244.3466	$244.35	$244.35	$244.30
7 purchase totals =	$1,044.25		$1,144.6026	$1,144.62	$1,144.65	$1,144.60