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	$152.96	4.639%	$160.0558	$160.06	$160.05	$160.10
Purchase #2	$76.25	9.209%	$83.2719	$83.27	$83.25	$83.30
Purchase #3	$188.41	4.465%	$196.8225	$196.82	$196.80	$196.80
Purchase #4	$228.27	4.280%	$238.04	$238.04	$238.05	$238.00
Purchase #5	$106.97	4.458%	$111.7387	$111.74	$111.75	$111.70
Purchase #6	$239.72	4.311%	$250.0543	$250.05	$250.05	$250.10
Purchase #7	$187.27	7.479%	$201.2759	$201.28	$201.30	$201.30
7 purchase totals =	$1,179.85		$1,241.2591	$1,241.26	$1,241.25	$1,241.30