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	$110.42	7.261%	$118.4376	$118.44	$118.45	$118.40
Purchase #2	$32.91	10.304%	$36.301	$36.30	$36.30	$36.30
Purchase #3	$92.70	7.658%	$99.799	$99.80	$99.80	$99.80
Purchase #4	$166.52	9.216%	$181.8665	$181.87	$181.85	$181.90
Purchase #5	$28.98	4.457%	$30.2716	$30.27	$30.25	$30.30
Purchase #6	$96.40	4.663%	$100.8951	$100.90	$100.90	$100.90
Purchase #7	$169.86	12.491%	$191.0772	$191.08	$191.10	$191.10
7 purchase totals =	$697.79		$758.6480	$758.66	$758.65	$758.70