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	$189.50	5.743%	$200.383	$200.38	$200.40	$200.40
Purchase #2	$85.55	8.666%	$92.9638	$92.96	$92.95	$93.00
Purchase #3	$68.92	3.687%	$71.4611	$71.46	$71.45	$71.50
Purchase #4	$226.51	9.234%	$247.4259	$247.43	$247.45	$247.40
Purchase #5	$207.47	11.568%	$231.4701	$231.47	$231.45	$231.50
Purchase #6	$249.31	8.644%	$270.8604	$270.86	$270.85	$270.90
Purchase #7	$153.67	11.372%	$171.1454	$171.15	$171.15	$171.10
7 purchase totals =	$1,180.93		$1,285.7097	$1,285.71	$1,285.70	$1,285.80