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	$10.35	5.428%	$10.9118	$10.91	$10.90	$10.90
Purchase #2	$163.74	5.575%	$172.8685	$172.87	$172.85	$172.90
Purchase #3	$227.59	10.151%	$250.6927	$250.69	$250.70	$250.70
Purchase #4	$85.50	5.454%	$90.1632	$90.16	$90.15	$90.20
Purchase #5	$239.83	13.293%	$271.7106	$271.71	$271.70	$271.70
Purchase #6	$64.98	11.661%	$72.5573	$72.56	$72.55	$72.60
Purchase #7	$194.72	5.424%	$205.2816	$205.28	$205.30	$205.30
7 purchase totals =	$986.71		$1,074.1857	$1,074.18	$1,074.15	$1,074.30