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	$35.92	4.861%	$37.6661	$37.67	$37.65	$37.70
Purchase #2	$84.82	5.398%	$89.3986	$89.40	$89.40	$89.40
Purchase #3	$31.61	4.235%	$32.9487	$32.95	$32.95	$32.90
Purchase #4	$154.95	9.412%	$169.5339	$169.53	$169.55	$169.50
Purchase #5	$181.57	9.534%	$198.8809	$198.88	$198.90	$198.90
Purchase #6	$238.33	4.223%	$248.3947	$248.39	$248.40	$248.40
Purchase #7	$116.53	11.834%	$130.3202	$130.32	$130.30	$130.30
7 purchase totals =	$843.73		$907.1431	$907.14	$907.15	$907.10