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	$38.40	12.323%	$43.132	$43.13	$43.15	$43.10
Purchase #2	$35.70	7.499%	$38.3771	$38.38	$38.40	$38.40
Purchase #3	$74.28	11.526%	$82.8415	$82.84	$82.85	$82.80
Purchase #4	$244.31	8.192%	$264.3239	$264.32	$264.30	$264.30
Purchase #5	$238.65	6.720%	$254.6873	$254.69	$254.70	$254.70
Purchase #6	$67.87	3.398%	$70.1762	$70.18	$70.20	$70.20
Purchase #7	$233.72	11.791%	$261.2779	$261.28	$261.30	$261.30
7 purchase totals =	$932.93		$1,014.8159	$1,014.82	$1,014.90	$1,014.80