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	$147.58	7.824%	$159.1267	$159.13	$159.15	$159.10
Purchase #2	$73.26	4.543%	$76.5882	$76.59	$76.60	$76.60
Purchase #3	$78.69	13.657%	$89.4367	$89.44	$89.45	$89.40
Purchase #4	$189.61	11.851%	$212.0807	$212.08	$212.10	$212.10
Purchase #5	$211.34	11.254%	$235.1242	$235.12	$235.10	$235.10
Purchase #6	$181.60	4.248%	$189.3144	$189.31	$189.30	$189.30
Purchase #7	$72.38	13.530%	$82.173	$82.17	$82.15	$82.20
7 purchase totals =	$954.46		$1,043.8439	$1,043.84	$1,043.85	$1,043.80