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	$96.51	4.373%	$100.7304	$100.73	$100.75	$100.70
Purchase #2	$103.76	7.322%	$111.3573	$111.36	$111.35	$111.40
Purchase #3	$193.51	10.269%	$213.3815	$213.38	$213.40	$213.40
Purchase #4	$48.25	6.272%	$51.2762	$51.28	$51.30	$51.30
Purchase #5	$238.45	12.361%	$267.9248	$267.92	$267.90	$267.90
Purchase #6	$67.49	13.217%	$76.4102	$76.41	$76.40	$76.40
Purchase #7	$175.72	13.802%	$199.9729	$199.97	$199.95	$200.00
7 purchase totals =	$923.69		$1,021.0533	$1,021.05	$1,021.05	$1,021.10