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	$223.53	7.478%	$240.2456	$240.25	$240.25	$240.20
Purchase #2	$195.33	9.695%	$214.2672	$214.27	$214.25	$214.30
Purchase #3	$46.41	4.397%	$48.4506	$48.45	$48.45	$48.50
Purchase #4	$61.85	6.120%	$65.6352	$65.64	$65.65	$65.60
Purchase #5	$92.64	7.337%	$99.437	$99.44	$99.45	$99.40
Purchase #6	$125.38	4.843%	$131.4522	$131.45	$131.45	$131.50
Purchase #7	$240.64	4.781%	$252.145	$252.15	$252.15	$252.10
7 purchase totals =	$985.78		$1,051.6328	$1,051.65	$1,051.65	$1,051.60