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	$200.73	10.515%	$221.8368	$221.84	$221.85	$221.80
Purchase #2	$144.34	6.641%	$153.9256	$153.93	$153.95	$153.90
Purchase #3	$88.30	7.483%	$94.9075	$94.91	$94.90	$94.90
Purchase #4	$77.41	10.177%	$85.288	$85.29	$85.30	$85.30
Purchase #5	$186.33	5.668%	$196.8912	$196.89	$196.90	$196.90
Purchase #6	$233.92	4.766%	$245.0686	$245.07	$245.05	$245.10
Purchase #7	$136.56	4.280%	$142.4048	$142.40	$142.40	$142.40
7 purchase totals =	$1,067.59		$1,140.3225	$1,140.33	$1,140.35	$1,140.30