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	$247.79	6.198%	$263.148	$263.15	$263.15	$263.10
Purchase #2	$85.44	8.251%	$92.4897	$92.49	$92.50	$92.50
Purchase #3	$43.42	8.601%	$47.1546	$47.15	$47.15	$47.20
Purchase #4	$167.77	8.352%	$181.7822	$181.78	$181.80	$181.80
Purchase #5	$188.49	4.150%	$196.3123	$196.31	$196.30	$196.30
Purchase #6	$209.82	9.587%	$229.9354	$229.94	$229.95	$229.90
Purchase #7	$212.81	12.250%	$238.8792	$238.88	$238.90	$238.90
7 purchase totals =	$1,155.54		$1,249.7014	$1,249.70	$1,249.75	$1,249.70