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	$52.27	13.381%	$59.2642	$59.26	$59.25	$59.30
Purchase #2	$60.93	6.777%	$65.0592	$65.06	$65.05	$65.10
Purchase #3	$8.33	11.754%	$9.3091	$9.31	$9.30	$9.30
Purchase #4	$68.27	10.233%	$75.2561	$75.26	$75.25	$75.30
Purchase #5	$99.64	10.117%	$109.7206	$109.72	$109.70	$109.70
Purchase #6	$53.66	12.534%	$60.3857	$60.39	$60.40	$60.40
Purchase #7	$115.50	6.762%	$123.3101	$123.31	$123.30	$123.30
7 purchase totals =	$458.60		$502.3050	$502.31	$502.25	$502.40