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	10.144%	$81.4184	$81.42	$81.40	$81.40
Purchase #2	$212.97	11.344%	$237.1293	$237.13	$237.15	$237.10
Purchase #3	$11.61	5.612%	$12.2616	$12.26	$12.25	$12.30
Purchase #4	$147.81	7.761%	$159.2815	$159.28	$159.30	$159.30
Purchase #5	$243.67	8.846%	$265.225	$265.23	$265.25	$265.20
Purchase #6	$66.43	9.552%	$72.7754	$72.78	$72.80	$72.80
Purchase #7	$196.81	11.459%	$219.3625	$219.36	$219.35	$219.40
7 purchase totals =	$953.22		$1,047.4537	$1,047.46	$1,047.50	$1,047.50