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	$42.71	7.119%	$45.7505	$45.75	$45.75	$45.80
Purchase #2	$128.84	5.172%	$135.5036	$135.50	$135.50	$135.50
Purchase #3	$182.28	8.847%	$198.4063	$198.41	$198.40	$198.40
Purchase #4	$232.59	13.431%	$263.8292	$263.83	$263.85	$263.80
Purchase #5	$195.39	12.258%	$219.3409	$219.34	$219.35	$219.30
Purchase #6	$128.69	7.797%	$138.724	$138.72	$138.70	$138.70
Purchase #7	$82.67	8.799%	$89.9441	$89.94	$89.95	$89.90
7 purchase totals =	$993.17		$1,091.4986	$1,091.49	$1,091.50	$1,091.40