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	$152.30	10.504%	$168.2976	$168.30	$168.30	$168.30
Purchase #2	$120.49	6.187%	$127.9447	$127.94	$127.95	$127.90
Purchase #3	$67.91	12.323%	$76.2785	$76.28	$76.30	$76.30
Purchase #4	$233.35	6.302%	$248.0557	$248.06	$248.05	$248.10
Purchase #5	$62.89	4.772%	$65.8911	$65.89	$65.90	$65.90
Purchase #6	$115.39	4.646%	$120.751	$120.75	$120.75	$120.80
Purchase #7	$186.41	4.160%	$194.1647	$194.16	$194.15	$194.20
7 purchase totals =	$938.74		$1,001.3833	$1,001.38	$1,001.40	$1,001.50