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	$205.72	8.226%	$222.6425	$222.64	$222.65	$222.60
Purchase #2	$45.67	13.721%	$51.9364	$51.94	$51.95	$51.90
Purchase #3	$64.54	10.661%	$71.4206	$71.42	$71.40	$71.40
Purchase #4	$104.25	12.516%	$117.2979	$117.30	$117.30	$117.30
Purchase #5	$175.28	3.297%	$181.059	$181.06	$181.05	$181.10
Purchase #6	$166.32	11.318%	$185.1441	$185.14	$185.15	$185.10
Purchase #7	$210.92	13.494%	$239.3815	$239.38	$239.40	$239.40
7 purchase totals =	$972.70		$1,068.8820	$1,068.88	$1,068.90	$1,068.80