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	$58.38	7.269%	$62.6236	$62.62	$62.60	$62.60
Purchase #2	$172.74	12.326%	$194.0319	$194.03	$194.05	$194.00
Purchase #3	$225.55	3.706%	$233.9089	$233.91	$233.90	$233.90
Purchase #4	$98.83	11.857%	$110.5483	$110.55	$110.55	$110.50
Purchase #5	$35.76	12.793%	$40.3348	$40.33	$40.35	$40.30
Purchase #6	$129.49	7.773%	$139.5553	$139.56	$139.55	$139.60
Purchase #7	$229.28	3.849%	$238.105	$238.11	$238.10	$238.10
7 purchase totals =	$950.03		$1,019.1078	$1,019.11	$1,019.10	$1,019.00