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	$168.98	3.118%	$174.2488	$174.25	$174.25	$174.20
Purchase #2	$30.77	8.399%	$33.3544	$33.35	$33.35	$33.40
Purchase #3	$138.75	6.506%	$147.7771	$147.78	$147.80	$147.80
Purchase #4	$92.25	3.275%	$95.2712	$95.27	$95.25	$95.30
Purchase #5	$82.56	8.324%	$89.4323	$89.43	$89.45	$89.40
Purchase #6	$235.28	8.666%	$255.6694	$255.67	$255.65	$255.70
Purchase #7	$184.81	11.170%	$205.4533	$205.45	$205.45	$205.50
7 purchase totals =	$933.40		$1,001.2065	$1,001.20	$1,001.20	$1,001.30