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	$245.48	3.669%	$254.4867	$254.49	$254.50	$254.50
Purchase #2	$233.64	12.784%	$263.5085	$263.51	$263.50	$263.50
Purchase #3	$73.93	11.362%	$82.3299	$82.33	$82.35	$82.30
Purchase #4	$78.54	8.702%	$85.3746	$85.37	$85.35	$85.40
Purchase #5	$145.41	3.376%	$150.319	$150.32	$150.30	$150.30
Purchase #6	$130.25	3.871%	$135.292	$135.29	$135.30	$135.30
Purchase #7	$78.59	4.255%	$81.934	$81.93	$81.95	$81.90
7 purchase totals =	$985.84		$1,053.2447	$1,053.24	$1,053.25	$1,053.20