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	$229.73	13.813%	$261.4626	$261.46	$261.45	$261.50
Purchase #2	$153.81	13.357%	$174.3544	$174.35	$174.35	$174.40
Purchase #3	$7.56	12.840%	$8.5307	$8.53	$8.55	$8.50
Purchase #4	$124.77	12.470%	$140.3288	$140.33	$140.35	$140.30
Purchase #5	$28.41	10.306%	$31.3379	$31.34	$31.35	$31.30
Purchase #6	$127.64	3.145%	$131.6543	$131.65	$131.65	$131.70
Purchase #7	$96.77	3.796%	$100.4434	$100.44	$100.45	$100.40
7 purchase totals =	$768.69		$848.1121	$848.10	$848.15	$848.10