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	$115.31	10.246%	$127.1247	$127.12	$127.10	$127.10
Purchase #2	$233.56	7.450%	$250.9602	$250.96	$250.95	$251.00
Purchase #3	$63.73	13.473%	$72.3163	$72.32	$72.30	$72.30
Purchase #4	$188.55	13.135%	$213.316	$213.32	$213.30	$213.30
Purchase #5	$169.92	6.231%	$180.5077	$180.51	$180.50	$180.50
Purchase #6	$64.43	7.321%	$69.1469	$69.15	$69.15	$69.10
Purchase #7	$218.45	5.202%	$229.8138	$229.81	$229.80	$229.80
7 purchase totals =	$1,053.95		$1,143.1856	$1,143.19	$1,143.10	$1,143.10