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	$50.51	4.496%	$52.7809	$52.78	$52.80	$52.80
Purchase #2	$73.88	11.553%	$82.4154	$82.42	$82.40	$82.40
Purchase #3	$19.71	13.485%	$22.3679	$22.37	$22.35	$22.40
Purchase #4	$211.78	3.488%	$219.1669	$219.17	$219.15	$219.20
Purchase #5	$196.91	9.329%	$215.2797	$215.28	$215.30	$215.30
Purchase #6	$212.98	3.213%	$219.823	$219.82	$219.80	$219.80
Purchase #7	$107.82	9.763%	$118.3465	$118.35	$118.35	$118.30
7 purchase totals =	$873.59		$930.1803	$930.19	$930.15	$930.20