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	$175.32	13.177%	$198.4219	$198.42	$198.40	$198.40
Purchase #2	$224.28	4.322%	$233.9734	$233.97	$233.95	$234.00
Purchase #3	$125.41	4.546%	$131.1111	$131.11	$131.10	$131.10
Purchase #4	$38.85	12.541%	$43.7222	$43.72	$43.70	$43.70
Purchase #5	$15.74	8.814%	$17.1273	$17.13	$17.15	$17.10
Purchase #6	$241.69	9.451%	$264.5321	$264.53	$264.55	$264.50
Purchase #7	$198.73	11.739%	$222.0589	$222.06	$222.05	$222.10
7 purchase totals =	$1,020.02		$1,110.9469	$1,110.94	$1,110.90	$1,110.90