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	$73.92	7.719%	$79.6259	$79.63	$79.65	$79.60
Purchase #2	$53.59	3.388%	$55.4056	$55.41	$55.40	$55.40
Purchase #3	$164.70	6.298%	$175.0728	$175.07	$175.05	$175.10
Purchase #4	$220.36	10.419%	$243.3193	$243.32	$243.30	$243.30
Purchase #5	$250.27	8.223%	$270.8497	$270.85	$270.85	$270.80
Purchase #6	$209.56	11.569%	$233.804	$233.80	$233.80	$233.80
Purchase #7	$62.35	5.670%	$65.8852	$65.89	$65.90	$65.90
7 purchase totals =	$1,034.75		$1,123.9625	$1,123.97	$1,123.95	$1,123.90