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	$225.75	5.349%	$237.8254	$237.83	$237.85	$237.80
Purchase #2	$90.29	12.265%	$101.3641	$101.36	$101.35	$101.40
Purchase #3	$6.41	11.535%	$7.1494	$7.15	$7.15	$7.10
Purchase #4	$98.72	6.342%	$104.9808	$104.98	$105.00	$105.00
Purchase #5	$170.29	10.558%	$188.2692	$188.27	$188.25	$188.30
Purchase #6	$209.42	9.604%	$229.5327	$229.53	$229.55	$229.50
Purchase #7	$219.63	5.494%	$231.6965	$231.70	$231.70	$231.70
7 purchase totals =	$1,020.51		$1,100.8181	$1,100.82	$1,100.85	$1,100.80