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	$85.37	6.295%	$90.744	$90.74	$90.75	$90.70
Purchase #2	$246.64	13.256%	$279.3346	$279.33	$279.35	$279.30
Purchase #3	$77.49	13.653%	$88.0697	$88.07	$88.05	$88.10
Purchase #4	$176.31	5.555%	$186.104	$186.10	$186.10	$186.10
Purchase #5	$233.55	13.216%	$264.416	$264.42	$264.40	$264.40
Purchase #6	$189.64	13.506%	$215.2528	$215.25	$215.25	$215.30
Purchase #7	$33.54	10.415%	$37.0332	$37.03	$37.05	$37.00
7 purchase totals =	$1,042.54		$1,160.9543	$1,160.94	$1,160.95	$1,160.90