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	$215.81	5.121%	$226.8616	$226.86	$226.85	$226.90
Purchase #2	$84.90	7.256%	$91.0603	$91.06	$91.05	$91.10
Purchase #3	$155.91	5.201%	$164.0189	$164.02	$164.00	$164.00
Purchase #4	$127.54	3.396%	$131.8713	$131.87	$131.85	$131.90
Purchase #5	$48.53	12.173%	$54.4376	$54.44	$54.45	$54.40
Purchase #6	$141.40	13.746%	$160.8368	$160.84	$160.85	$160.80
Purchase #7	$21.33	6.695%	$22.758	$22.76	$22.75	$22.80
7 purchase totals =	$795.42		$851.8445	$851.85	$851.80	$851.90