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	$160.72	5.327%	$169.2816	$169.28	$169.30	$169.30
Purchase #2	$162.89	12.825%	$183.7806	$183.78	$183.80	$183.80
Purchase #3	$78.81	8.234%	$85.2992	$85.30	$85.30	$85.30
Purchase #4	$58.35	13.352%	$66.1409	$66.14	$66.15	$66.10
Purchase #5	$123.26	6.322%	$131.0525	$131.05	$131.05	$131.10
Purchase #6	$236.88	11.474%	$264.0596	$264.06	$264.05	$264.10
Purchase #7	$147.53	3.478%	$152.6611	$152.66	$152.65	$152.70
7 purchase totals =	$968.44		$1,052.2755	$1,052.27	$1,052.30	$1,052.40