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	$11.48	3.874%	$11.9247	$11.92	$11.90	$11.90
Purchase #2	$9.90	6.657%	$10.559	$10.56	$10.55	$10.60
Purchase #3	$110.62	11.532%	$123.3767	$123.38	$123.40	$123.40
Purchase #4	$81.27	6.846%	$86.8337	$86.83	$86.85	$86.80
Purchase #5	$120.96	4.504%	$126.408	$126.41	$126.40	$126.40
Purchase #6	$51.78	3.689%	$53.6902	$53.69	$53.70	$53.70
Purchase #7	$90.71	8.393%	$98.3233	$98.32	$98.30	$98.30
7 purchase totals =	$476.72		$511.1156	$511.11	$511.10	$511.10