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	$174.91	11.213%	$194.5227	$194.52	$194.50	$194.50
Purchase #2	$122.32	6.670%	$130.4787	$130.48	$130.50	$130.50
Purchase #3	$144.89	5.463%	$152.8053	$152.81	$152.80	$152.80
Purchase #4	$129.45	5.309%	$136.3225	$136.32	$136.30	$136.30
Purchase #5	$169.43	7.314%	$181.8221	$181.82	$181.80	$181.80
Purchase #6	$133.69	9.107%	$145.8651	$145.87	$145.85	$145.90
Purchase #7	$6.74	5.672%	$7.1223	$7.12	$7.10	$7.10
7 purchase totals =	$881.43		$948.9387	$948.94	$948.85	$948.90