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	$146.33	4.546%	$152.9822	$152.98	$153.00	$153.00
Purchase #2	$98.42	11.420%	$109.6596	$109.66	$109.65	$109.70
Purchase #3	$142.81	6.249%	$151.7342	$151.73	$151.75	$151.70
Purchase #4	$240.72	12.111%	$269.8736	$269.87	$269.85	$269.90
Purchase #5	$189.86	13.369%	$215.2424	$215.24	$215.25	$215.20
Purchase #6	$183.85	4.335%	$191.8199	$191.82	$191.80	$191.80
Purchase #7	$49.72	12.375%	$55.8729	$55.87	$55.85	$55.90
7 purchase totals =	$1,051.71		$1,147.1848	$1,147.17	$1,147.15	$1,147.20