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	$93.63	5.464%	$98.7459	$98.75	$98.75	$98.70
Purchase #2	$77.85	9.389%	$85.1593	$85.16	$85.15	$85.20
Purchase #3	$53.65	6.104%	$56.9248	$56.92	$56.90	$56.90
Purchase #4	$224.31	11.816%	$250.8145	$250.81	$250.80	$250.80
Purchase #5	$188.88	13.445%	$214.2749	$214.27	$214.25	$214.30
Purchase #6	$125.55	13.272%	$142.213	$142.21	$142.20	$142.20
Purchase #7	$176.34	13.559%	$200.2499	$200.25	$200.25	$200.20
7 purchase totals =	$940.21		$1,048.3823	$1,048.37	$1,048.30	$1,048.30